🐛 Bug Report: MCP Span Missing for stdio Transport Mode

[elinacse]

Which component is this bug for?

Traceloop SDK

📜 Description

As per MCP instrumentation these spans are expected
mcp.method.name
mcp.request.argument
mcp.request.id
mcp.response.value
mcp.session.init_options
But when running MCP server in stdio mode only RequestStreamWriter span is coming no ResponseStreamWriter span is present (mcp.response.value) span is missing and also mcp.session.init_options span is mising hence we are not getting the tool response details .

👟 Reproduction steps

1. Initialize MCP server with traceloop
2. Run mcp server in stdio mode
3. check in traceloop the particular span(ResponseStreamWriter -> mcp.response.value), mcp.session.init_options is missing

👍 Expected behavior

mcp.response.value ,mcp.session.init_options span should be present for stdio mode .

👎 Actual Behavior with Screenshots

Here in the picture root span is also missing

🤖 Python Version

3.13

📃 Provide any additional context for the Bug.

No response

👀 Have you spent some time to check if this bug has been raised before?

• I checked and didn't find similar issue

Are you willing to submit PR?

None

[nirga]

Thanks @elinacse! Do you mind sharing a minimal reproducible example?

[elinacse]

@nirga Here is the sample mcp server which I tested with Claude Desktop

weather.py

Here is the picture for the sample the route spna is missing and we only see RequestStreamWriter No ResponseStreamWriter is there .

CC: @gyliu513

[gyliu513]

@fali007 ^^

[elinacse]

#3383